The overall goal of Project 4 is to detemine how diabetes affects cardiac progenitor cell (CPC)-mediated myocardial repair after infarction and how CPC therapy could be optimized for the diabetic heart. Although stem cell therapy with CPCs offers new hope for the treatment of heart failure, the efficacy of stem cell therapy in diabetes remains uncertain. Our preliminary observations show that diabetes impairs CPC growth and differentiation, and in contrast to non-diabetic hearts, diabetic hearts do not benefit from CPC therapy. We propose that diabetes decreases CPC competence by inducing insulin resistance. Excessive nutrients in diabetes increase the production of reactive oxygen species (ROS) that triger inflammation and establish insulin resistance in CPCs. This in turn impairs their capacity to promote myocardial repair. To test this hypothesis, three specific aims are proposed. (1) To examine glucose transport and glucose and fattty acid metabolism in CPCs, we will measure the rates of glycolysis and fatty acid metabolism in lin-/kit+ CPCs isolated from the mouse heart, under basal condition and in the presence of high glucose and palmitic acid and determine how nutrient excess affects the fundamental parameters of CPC competence. To determine the effect of diabetes, we will isolate CPCs from db/db and high-fat fed mice and compare their competence with CPCs from non- diabetic mice. (2) To elucidate the mechanisms by which nutrient excess affects CPCs, we will examine the role of inflammation and oxidative stress in inducing insulin resistance and test the hypothesis that in conditions of nutrient excess or diabetes, hyperactivity of the mitochondrial electron transport chain leads to an increase in ROS production which triggers pro-inflammatory responses resulting in insulin resistance. (3) To determine the impact of diabetes on CPC-mediated myocardial repair, we will transplant diabetic CPCs in non-diabetic hearts and non-diabetic CPCs in diabetic hearts after myocardial infarction and measure changes in CPC-mediated changes in myocardial function and test whether anti-inflammatory or anti-oxidant interventions that resolve insulin resistance promote CPC mediated myocardial repair in the diabetic and non-diabetic hearts. RELEVANCE (See instructions): A majority of patients with heart failure have diabetes, yet the effects of diabetes on stem cell therapy are unknown. By providing new understanding of the underlying mechanisms by which diabetes affects stem cell therapy in heart failure and how stem cell therapy could be optimized for the diabetic heart, this project could lead to the development of new therapies for the treatment of heart failure in diabetic and non-diabetic patients..